From 3eb06f6ce3af65df4e9b3d8fc1d711fbfe7673b3 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Wed, 25 Jun 2025 11:34:32 +0000 Subject: [PATCH] arm64: cpufeature: Introduce MATCH_ALL_EARLY_CPUS capability type MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit For system-wide capabilities, the kernel has the SCOPE_SYSTEM type. Such capabilities are checked once the SMP boot has completed using the sanitised ID registers. However, there is a need for a new capability type similar in scope to the system one but with checking performed locally on each CPU during boot (e.g. based on MIDR_EL1 which is not a sanitised register). Introduce ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS which, together with ARM64_CPUCAP_SCOPE_LOCAL_CPU, ensures that such capability is enabled only if all early CPUs have it. For ease of use, define ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE which combines SCOPE_LOCAL_CPU, PERMITTED_FOR_LATE_CPUS and MATCH_ALL_EARLY_CPUS. Signed-off-by: Mikołaj Lenczewski Reviewed-by: Suzuki K Poulose Link: https://lore.kernel.org/r/20250625113435.26849-2-miko.lenczewski@arm.com Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/cpufeature.h | 23 +++++++++++ arch/arm64/kernel/cpufeature.c | 60 +++++++++++++++++++++++------ 2 files changed, 72 insertions(+), 11 deletions(-) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index c4326f1cb9176..155ebd040c55c 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -275,6 +275,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; #define ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU ((u16)BIT(5)) /* Panic when a conflict is detected */ #define ARM64_CPUCAP_PANIC_ON_CONFLICT ((u16)BIT(6)) +/* + * When paired with SCOPE_LOCAL_CPU, all early CPUs must satisfy the + * condition. This is different from SCOPE_SYSTEM where the check is performed + * only once at the end of the SMP boot on the sanitised ID registers. + * SCOPE_SYSTEM is not suitable for cases where the capability depends on + * properties local to a CPU like MIDR_EL1. + */ +#define ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS ((u16)BIT(7)) /* * CPU errata workarounds that need to be enabled at boot time if one or @@ -304,6 +312,16 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) +/* + * CPU feature detected at boot time and present on all early CPUs. Late CPUs + * are permitted to have the feature even if it hasn't been enabled, although + * the feature will not be used by Linux in this case. If all early CPUs have + * the feature, then every late CPU must have it. + */ +#define ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE \ + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ + ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU | \ + ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS) /* * CPU feature detected at boot time, on one or more CPUs. A late CPU @@ -391,6 +409,11 @@ static inline int cpucap_default_scope(const struct arm64_cpu_capabilities *cap) return cap->type & ARM64_CPUCAP_SCOPE_MASK; } +static inline bool cpucap_match_all_early_cpus(const struct arm64_cpu_capabilities *cap) +{ + return cap->type & ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS; +} + /* * Generic helper for handling capabilities with multiple (match,enable) pairs * of call backs, sharing the same capability bit. diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index b34044e20128b..f9c9471663220 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -3370,18 +3370,49 @@ static void update_cpu_capabilities(u16 scope_mask) scope_mask &= ARM64_CPUCAP_SCOPE_MASK; for (i = 0; i < ARM64_NCAPS; i++) { + bool match_all = false; + bool caps_set = false; + bool boot_cpu = false; + caps = cpucap_ptrs[i]; - if (!caps || !(caps->type & scope_mask) || - cpus_have_cap(caps->capability) || - !caps->matches(caps, cpucap_default_scope(caps))) + if (!caps || !(caps->type & scope_mask)) continue; - if (caps->desc && !caps->cpus) + match_all = cpucap_match_all_early_cpus(caps); + caps_set = cpus_have_cap(caps->capability); + boot_cpu = scope_mask & SCOPE_BOOT_CPU; + + /* + * Unless it's a match-all CPUs feature, avoid probing if + * already detected. + */ + if (!match_all && caps_set) + continue; + + /* + * A match-all CPUs capability is only set when probing the + * boot CPU. It may be cleared subsequently if not detected on + * secondary ones. + */ + if (match_all && !caps_set && !boot_cpu) + continue; + + if (!caps->matches(caps, cpucap_default_scope(caps))) { + if (match_all) + __clear_bit(caps->capability, system_cpucaps); + continue; + } + + /* + * Match-all CPUs capabilities are logged later when the + * system capabilities are finalised. + */ + if (!match_all && caps->desc && !caps->cpus) pr_info("detected: %s\n", caps->desc); __set_bit(caps->capability, system_cpucaps); - if ((scope_mask & SCOPE_BOOT_CPU) && (caps->type & SCOPE_BOOT_CPU)) + if (boot_cpu && (caps->type & SCOPE_BOOT_CPU)) set_bit(caps->capability, boot_cpucaps); } } @@ -3782,17 +3813,24 @@ static void __init setup_system_capabilities(void) enable_cpu_capabilities(SCOPE_ALL & ~SCOPE_BOOT_CPU); apply_alternatives_all(); - /* - * Log any cpucaps with a cpumask as these aren't logged by - * update_cpu_capabilities(). - */ for (int i = 0; i < ARM64_NCAPS; i++) { const struct arm64_cpu_capabilities *caps = cpucap_ptrs[i]; - if (caps && caps->cpus && caps->desc && - cpumask_any(caps->cpus) < nr_cpu_ids) + if (!caps || !caps->desc) + continue; + + /* + * Log any cpucaps with a cpumask as these aren't logged by + * update_cpu_capabilities(). + */ + if (caps->cpus && cpumask_any(caps->cpus) < nr_cpu_ids) pr_info("detected: %s on CPU%*pbl\n", caps->desc, cpumask_pr_args(caps->cpus)); + + /* Log match-all CPUs capabilities */ + if (cpucap_match_all_early_cpus(caps) && + cpus_have_cap(caps->capability)) + pr_info("detected: %s\n", caps->desc); } /* -- 2.47.2